Litter layers (Oie) as a calcium source of sugar maple seedlings in a northern hardwood forest
The role of the Oie horizon in calcium supply of sugar maple (Acer saccharum Marsh.) seedlings was evaluated. Forest floor Oie horizon was reciprocally transplanted on 1 m2 quadrats between a Ca-treated (W1) and a reference (W3) watershed, and sugar maple seeds were planted on the quadrats. The Oie horizon in W1 exhibited a greatly increased Ca:Sr molar ratio compared with the reference W3 (550 vs. 220), allowing distinction of this Ca source in seedling tissues. Foliage and fine roots of maple seedlings growing on quadrats in W3 with Oie transplanted from W1 exhibited Ca:Sr ratios intermediate between the Oie and underlying native soil horizons, demonstrating the role of Oie in seedling Ca nutrition. However, apparently strong and temporally changing discrimination of Ca and Sr in seedling uptake and internal transport confounded quantitative evaluation.